This invention relates to an apparatus for transporting sheets, for instance from paper or other material that is form-retaining in its plane, along a transport track with a bend passing around a transport roller, between a first portion and a second, differently directed portion of the transport track.
It is known, for transporting sheets of paper around a bend, to use a sheet track, of which the bend passes through a particular angular range around a portion of the circumference of one or more transport rollers. For guiding the individual sheets or stacked sheets around the bend, a sheet guiding surface can be used which is situated within the angular range at a small, constant distance from the circumferential portion of the transport roller. A drawback of such a sheet track is that it is only suitable for transporting sheets or stacked sets of sheets having a thickness within a narrow range. When sheets are too thin, they are not reliably passed through, and if a set is too thin, moreover, different sheets pass around the bend along arcs having relatively greatly different radii—and hence along paths of relatively greatly different lengths—which gives rise to mutual shifting of the sheets. If a sheet or set of sheets is too thick, it will jam or at least there is a considerable risk it will jam.
It is also known, for guiding sheets or stacked sets of sheets around the bend, to use sheet guiding rollers circumferentially distributed over the angular range, each defining a nip with the transport roller against which they abut. In operation, the paper is then guided through the bend in that it is guided through the series of successive nips between the circumferential section and the rollers cooperating with it. A drawback of this construction, however, is that it is complex and costly. A further drawback is that each time when stacked sets of sheets are being guided through the nip, the outer sheets, and especially the sheets on the side of the relatively small rollers, are displaced, with respect to the other sheets, against the transport direction. Such small displacements add up to mutually displaced sheets which, in particular if the sheets are subsequently folded, give the set of sheets a sloppy appearance.